56 GENERAL BIOLOGY. 



Make an outline sketch of the section, omitting 

 cell-details. 

 With D 2 study the cell-structures as far as 



they can be made out. 

 In the ectoderm : 



(a) Large vacuolated ectoderm-cells ; the nu- 



clei can be seen in some sections. 



(b) Between the large ectoderm-cells rows of 



smaller deeply stained cells, the inter- 

 stitial cells. Many of these are devel- 

 oping into : 



(c) Cnidoblasts. 



(d) A row of minute bodies like dots lying 



along the outer side of the support- 

 ing lamella : sections of the contractile 

 processes of the large ectoderm-cells. 



Between ectoderm and entoderm the thin, 

 structureless, supporting lamella. 



In the entoderm : 



(e) A single layer of large, much vacuolated 



cells. (What is the explanation of the 

 appearance in the section of several 

 layers of cells ?) 

 (/) Small gland-cells among the ordinary 



entodermal cells. 

 /Sketch accurately part of the section a few cells in 



width. 

 Longitudinal Section. 



